Final answer:
You should avoid increasing intrathoracic pressure through activities that require straining or holding one's breath, which can lead to decreased cardiac output and orthostatic hypotension, characterized by dizziness or lightheadedness upon standing.
Step-by-step explanation:
Individuals should avoid actions that increase intrathoracic pressure, as it can lead to a decrease in cardiac output and reduced blood flow to critical organs such as the heart and brain. This can result in orthostatic hypotension, which happens when blood pressure drops upon standing and results in dizziness, lightheadedness, or a 'head rush'. Activities that increase intrathoracic pressure include straining during bowel movements, heavy lifting, or any activity that causes forceful breathing or holding one's breath, commonly referred to as the Valsalva maneuver. Additionally, avoiding the rapid inhalation of substances like CO that can reduce the oxygen-carrying capacity of blood is also necessary to prevent a decrease in oxygen available to organs and tissues.
Orthostatic hypotension occurs when there is a failure in the sympathetic reflex that usually helps maintain blood flow to the brain upon standing. The reflex involves the speeding up of the heart rate and constriction of blood vessels to maintain cerebral perfusion against gravity. When this reflex doesn't work quickly or effectively enough, orthostatic hypotension can occur, leading to temporary neurological impairments. Staying hydrated, moving slowly from sitting to standing, and understanding any underlying health conditions that could contribute to this issue are important for preventing orthostatic hypotension.